This research program is designed to identify and characterize proteinase inhibitors produced by lymphocytes and to determine their role in immunoregulation. An immediate goal is to characterize the inhibitors recently discovered in our laboratory, i.e., a low MW inhibitor produced by normal rabbit T cells, a high MW inhibitor produced by human T cell line (C91/PL) and inhibitors produced by a mouse T cell line (WEHI 7.1) and a human null cell line (NALM-16). Additional human and mouse lymphocyte lines will be tested for their ability to produce proteinase inhibitors so as to determine the spectrum of inhibitors produced and the phenotype of the lymphocytes producing them. The inhibitors will be initially characterized by determining the specificity for enzyme inhibition, the approximate molecular weight, and some chemical properties. Purified of inhibitors will be obtained by various preparative methods including SDS-PAGE and will be used to generate polyclonal and monoclonal Abs so as to develop immunoassays and to facilitate further purification. Biochemical studies will be done to determine the basic structure of the inhibitor molecules with respect to amino acids, carbohydrate, disulfide bonds and phosphoryl groups. Functional studies will be done by determining the effect of the inhibitors on immune reactions that are known to involve enzyme activation. Selected physiological and pathological conditions as well as in vitro cell culture conditions which result in the production of proteinase inhibitors by lymphocytes will be investigated, such as allogeneic stimulation, graft vs host reactions, autoimmunity, and mixed lymphocyte reactions. Lymphocyte populations from mice which produce a proteinase inhibitor will be used to develop new cell lines or hybridomas so as to establish a continuous source of the same inhibitor for analysis. Since enzymes have a prominent role in the pathogenesis of inflammation, e.g. in rheumatoid arthritis, the proteinase inhibitors produced by lymphocytes may be anti-inflammatory biological agents with potential therapeutic value. Another possibility is that proteinase inhibitors may have a role in the control of metastatic tumor growth, e.g. perhaps some inhibitors may slow tumor growth by specifically blocking the enzymes produced by some tumors whreas other inhibitors may facilitate metastases by specifically blocking the proteinase-mediated cytolytic activity of cytotoxic T cells.